When referring to WCAG 2.0 from another standard with a "should" statement

When referencing WCAG 2.0 from within a should statement in a standard (or advisory statement in a regulation), then the full WCAG 2.0 should be referenced. This would mean that all three levels of WCAG 2.0 should be considered but that none are required. The format for referencing WCAG 2.0 from a "should" statement therefore, is:

When referring to WCAG 2.0 from another standard with a "shall or must" statement

When citing WCAG 2.0 as part of a requirement (e.g., a shall or must
statement in a standard or regulation), the reference must include the specific parts of WCAG 2.0 that are intended to be required. When referencing WCAG 2.0 in this manner, the following rules apply:

Conformance at any level of WCAG 2.0 requires that all of the Level A Success Criteria be met. References to WCAG 2.0 conformance cannot be for any subset of Level A.

Beyond Level A, a "shall or must" reference may include any subset of provisions in Levels AA and AAA. For example, "all of Level A and [some specific list of Success Criteria in Level AA and Level AAA]" be met.

If Level AA conformance to WCAG 2.0 is specified, then all Level A and all Level AA Success Criteria must be met.

If Level AAA conformance to WCAG 2.0 is specified, then all Level A, all Level AA, and all Level AAA Success Criteria must be met.

Note 1:
It is not recommended that Level AAA conformance ever be required for entire sites as a general policy because it is not possible to satisfy all Level AAA Success Criteria for some content.

Note 2:
The sets of Success Criteria defined in WCAG are interdependent and individual Success Criteria rely on each other's definitions in ways which may not be immediately obvious to the reader. Any set of Success Criteria must include all of the Level A provisions.

Referring to content from WCAG support documents

Techniques, which are listed in Understanding WCAG 2.0 and described in other supporting documents, are not part of the normative WCAG 2.0 Recommendation and should not be cited using the citation for the WCAG 2.0 Recommendation itself. References to techniques in support documents should be cited separately.

Techniques can be cited based on the individual Technique document or on the master WCAG 2.0 Techniques document. For example, the technique "Using alt attributes on img elements" could be cited as

Techniques are not designed to be referenced as "required" from any standard or regulation.Standards and regulations should not make any specific technique mandatory, though they may choose to recommend techniques.